Abstract

The removal of toxic metal ions using modified cellulose acetate (CA) membranes from aqueous solutions has been systematically investigated. CA ultrafiltration membranes were prepared by the phase inversion technique, using high performance thermoplastic poly (ether-ether-sulfone) (PEES) as the modification agent and polyethylene glycol (PEG-600) as the pore former. Toxic heavy metal ions, such as copper, nickel, zinc and cadmium, were subjected to separation by the blend membranes by complexing them with the polymeric ligand polyethyleneimine (PEI). The fouling resistant ability of the membranes was evaluated by bovine serum albumin (BSA) as a model foulant and flux recovery ratio and flux decline rate were calculated. The effects of different proportions of PEES (0–30 wt %) incorporated into the CA on the morphology, hydrophilicity, compatibility, degree of crystallinity, fouling propensity and toxic metal ions separation of the prepared membranes, were evaluated. The surface chemistry of the membranes was assessed by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Ultrafiltration characterisations, such as compaction, pure water flux (PWF), water content, membrane hydraulic resistance, porosity and molecular weight cut-off (MWCO) were investigated. Attempts have been made to correlate the performances of the membranes with their morphology. The scanning electron microscopy (SEM) studies revealed that the incorporation of PEES resulted in the formation of a spongy sub-layer, and increased the connectivity of pores between the sub-layer and the bottom layer. It is worth mentioning that the separation efficiency of these membranes arising from the fine dispersion of PEES in the CA matrix, obviously offers immense potential in industrial separations. Thus, it was found that the CA/PEES blend ultrafiltration membranes demonstrated better performance, compared to the membranes prepared from pure cellulose acetate.